In a long-term evolution (LTE) system, a user equipment (UE) receives downlink data transmitted by a base station, decodes the downlink data and obtains a response signal of the downlink data based on the decoding result, then transmits uplink control information containing the response signal in a physical uplink control channel (PUCCH), so that the base station can judge whether the data transmission is correct or wrong according to the uplink control information and hence judge whether data retransmission is needed. Wherein, the uplink control information comprises response signals for downlink data, such as acknowledgement (ACK)/negative acknowledgement (NACK)/discontinuous transmission (DTX), and channel state information (CSI), etc., wherein the ACK denotes that the data are correctly received, NACK denotes that the data are wrongly received, and DTX denotes that the UE receives no downlink control data, that is, receives no control signaling for scheduling downlink data transmission.
The response signals transmitted in the PUCCH correspond respectively to a physical channel resource, a time domain sequence and a frequency domain sequence, these three resources being associated with two parameters. One parameter is parameter N1 configured by a high layer of the system and is the same for all the UEs in all cells, and the other parameter is associated with an index of a first control channel element (CCE) contained in a physical downlink control channel (PDCCH) used for scheduling the downlink data to which the response signals correspond. In particular, N1 determines a starting position of the PUCCH used for transmitting the response signals, in the frequency domain in an uplink subframe, and this parameter is shared by all the UE or mobile stations in the cells; and the index of the first CCE of the PDCCH, together with the starting position, determine the physical resources and sequence resources actually used by the UE scheduled in the PDCCH in transmitting uplink control signaling, as shown in FIG. 1.
FIG. 2 is a schematic diagram of the timing sequence of response signal transmission of an LTE FDD (frequency division duplexing) system. For an LTE FDD system, uplink subframes correspond to downlink subframes one by one. Namely, for any one of the UE in the system, in an uplink subframe, only a response signal value of the data in a downlink subframe corresponding to the uplink subframe is transmitted. The data transmitted in a downlink subframe contains at most two transmission blocks (TBs), that means, there exist response signals with two bits. The response signals with two bits need to be modulated into QPSK (quadrature phase shift keying) symbols before transmission, and then are mapped into corresponding physical resources and sequence resources. The timing sequence of ACK/NACK transmission of an LTE FDD system is as shown in FIG. 2.
FIG. 3 is a schematic diagram of the timing sequence of response signal transmission of an LTE TDD (time division duplexing) system. In LTE TDD system, 7 types of uplink and downlink subframe configuration are defined. In most of the subframe configuration, one uplink subframe corresponds to multiple downlink subframes in many cases; that is, for any one of the UE in the system, in an uplink subframe, response signal values of the data in multiple downlink subframes corresponding to the uplink subframe need to be transmitted. The timing sequence of transmission of ACK/NACK to which certain uplink and downlink subframe configuration corresponds of an LTE TDD system is as shown in FIG. 3.
Currently, a method called channel selection is used in an LTE TDD system to transmit response signals, to which the data in multiple downlink subframe correspond, in an uplink subframe. The method comprises: if two TBs are contained in the downlink subframe, bundling the response signals of the two TBs; for example, when all the response signals are ACK, the result is still ACK after bundling, otherwise, the result is NACK; and then determining modulated symbol values and corresponding physical resources and sequence resources by looking up a table based on the bundled response signals.
Table 1 shows a response signal feedback method when two downlink subframes correspond to one uplink subframe. As shown in Table 1, if the response signals detected by the UE in the two subframes are (ACK, ACK), the lowest CCE index n1 of the PDCCH used for scheduling the UE to perform downlink signal transmission, in the first subframe is chosen for uplink physical resources and sequence resources mapping, with a value of modulation symbol being −1, and if the response signals to which the two subframes correspond are (ACK, NACK/DTX), the lowest CCE index n0 of the PDCCH in the 0th subframe is chosen for uplink physical resources and sequence resources mapping, with a value of modulation symbol being j, and other channel selection schemes may be deducted by analogy according to Table 1. In general, the number of resources needed in channel selection is equal to the number of bits of the response signals; for example, if the numbers of the response signals are 2, 3 or 4 bits, 2, 3 or 4 resources are needed respectively.
TABLE 1A channel selection scheme for responsesignals with 2 bits in an LTE systemResponse signal 1, Response signal 2Resourcesb(0), b(1)ACK, ACKn1−1  ACK, NACK/DTXn0−j  NACK/DTX, ACKn11NACK/DTX, NACKn1jNACK, DTXn0jDTX, DTXN/AN/A
It can be seen from above that in an LTE TDD system, as bundling of response signals is used, an available resource may be obtained from each downlink subframe containing data transmission. Hence, the resources are sufficient when the response signals values fed back are mapped to the resources.
In an LTE-advanced (LTE-A) system, carrier aggregation (CA) is used in data transmission, in which the uplink and downlink containing multiple component carriers (CC), and uplink data transmission and downlink data transmission may be scheduled in each component carrier for a mobile station in the system. The system configures each UE with a downlink primary component carrier (PCC) and multiple secondary component carriers (SCCs). The data transmitted in the PCC and SCCs is scheduled respectively.
In the LTE-A system, for any UE, control information, such as response signals of the data of each downlink component carrier and channel state information (CSI) of the downlink component carrier, etc., to which all the configured downlink SCCs of the UE correspond, is fed back in the uplink PCC of the UE. This is similar to the LTE TDD, that is, the mobile station needs to feed back response signals values of the data in multiple downlink subframes in an uplink subframe of one PCC, the downlink subframes belonging to different downlink component carriers (CCs).
However, in the implementation of the present invention, the inventor found following defects existing in the prior art of an LTE-A system, when carrier aggregation scheme is adopted, as resources to which a PCC corresponds are pre-configured, when a base station transmits data by using SCCs, a case of insufficient resources exists because bundling is not adopted in accordance with the requirement of a single carrier.
For example, when a mobile station is configured with 2 CCs, that is, a PCC and a PCC, and 2 TBs are transmitted in each of the CCs, 4 response signals values are needed to be fed back and 4 resources are needed for selection; while in a general case, resources to which a PCC corresponds are normally pre-configured, in this case, if mapping is performed by using only the lowest CCE index of the PDCCH in each CC, the number of the available resources is only 2.
There is no effective solution for the case of resources insufficient till now.
Following documents are listed for the easy understanding of the present invention and conventional technologies, which are incorporated herein by reference as they are fully stated in this text.
1) CN101594211A, published in Dec. 2, 2009, and entitled Method for sending correct/wrong response message in multicarrier system with big bandwidth;
2) CN101588226A, published in Nov. 25, 2009, and entitled Terminal in large bandwidth multi-carrier system and a sending method of response message; and
3) WO2010/050688A2, entitled Method of HARQ acknowledgement transmission and transport block retransmission in a wireless communication system.